forsmark site investigation â€“ difference flow logging

Forsmark site investigation – Difference flow logging Svensk Kärnbränslehantering AB Swedish Nuclear Fuel and Waste Management Co Box 5864 SE-102 40 Stockholm Sweden Tel 08-459 84 00 +46 8 459 84 00 Fax 08-661 57 19 +46 8 661 57 19
P-07-85
Juha Väisäsvaara, Janne Pekkanen
Juha Väisäsvaara, Janne Pekkanen
Keywords: Forsmark, Hydrogeology, Hydraulic tests, Difference flow measurements, KFM11A, AP PF 400-06-096.
This report concerns a study which was conducted for SKB. The conclusions and viewpoints presented in the report are those of the authors and do not necessarily coincide with those of the client.
Data in SKB’s database can be changed for different reasons. Minor changes in SKB’s database will not necessarily result in a revised report. Data revisions may also be presented as supplements, available at www.skb.se.

Abstract
Difference flow logging is a swift method for the determination of the transmissivity and the hydraulic head in borehole sections and fractures/fracture zones in core drilled boreholes. This report presents the main principles of the methods as well as the results of measurements carried out in borehole KFM11A at Forsmark, Sweden, in November and December 2006 and April 2007, using Posiva Flow Log. Posiva Flow Log is a multipurpose measurement instrument developed by PRG-Tec Oy for the use of Posiva Oy. The primary aim of the measurements was to determine the position and flow rate of flow yielding fractures in the borehole prior to groundwater sampling.
The borehole was only partially measured due to instable sections at c. 500 m borehole length.
The first flow logging measurements were done with a 5 m test section by moving the measurement tool in 0.5 m steps. This method was used to flow log the measurable part of the borehole during natural (un-pumped) as well as pumped conditions. The flow measurements were repeated at the location of detected flow anomalies using a 1 m long test section, which was moved in 0.1 m steps.
Length calibration was made based on length marks milled into the borehole wall at accurately determined positions along the borehole. The length marks were detected by caliper measurements and by single-point resistance measurements using sensors connected to the flow logging tool.
A high-resolution absolute pressure sensor was used to measure the absolute total pressure along the borehole. These measurements were carried out together with the flow measurements.
The electric conductivity (EC) and temperature of borehole water were also measured. The EC measurements were used to study the occurrence of saline water in the borehole during natural as well as pumped conditions. The EC of fracture-specific water was also measured (1.0 m test section) for a selection of fractures.

Sammanfattning
Differensflödesloggning är en snabb metod för bestämning av transmissiviteten och hydraulisk tryckhöjd i borrhålssektioner och sprickor/sprickzoner i kärnborrhål. Denna rapport presenterar huvudprinciperna för metoden och resultat av mätningar utförda i borrhål KFM11A i Forsmark, Sverige, i november och december 2006 och april 2007 med Posiva flödesloggningsmetod (Posiva Flow Log). Posiva Flow Log är ett mångsidigt instrument utväcklad av PRG-Tec Oy för Posiva Oy. Det primära syftet med mätningarna var att bestämma läget och flödet för vattenförande sprickor i borrhålet före grundvattenprovtagning.
Borrhålet undersöktes endast delvis på grund av instabila sektioner vid ca 500 m borrhålslängd.
Flödet till eller från en 5 m lång testsektion (som förflyttades successivt med 0,5 m) mättes i borrhålet under såväl naturliga (icke-pumpade) som pumpade förhållanden. Flödesmätningarna upprepades vid lägena för de detekterade flödesanomalierna med en 1 m lång testsektion som förflyttades successivt i steg om 0,1 m.
Längdkalibrering gjordes baserad på längdmärkena som frästs in i borrhålsväggen vid noggrant bestämda positioner längs borrhålet. Längdmärkena detekterades med caliper och punktresistans- mätningar med hjälp av sensorer anslutna på flödesloggningssonden.
En högupplösande absoluttryckgivare användes för att mäta det absoluta totala trycket längs borrhålet. Dessa mätningar utfördes tillsammans med flödesmätningarna.
Elektrisk konduktivitet och temperatur på borrhålsvattnet mättes också. EC-mätningarna använ- des för att studera förekomsten av saltvatten i borrhålet under såväl naturliga som pumpade förhållanden. Även EC på vattnet i ett antal utvalda sprickor mättes (1 m lång testsektion).
Återhämtningen av grundvattennivån mättes efter att pumpningen i hålet avslutades.
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Contents
2 Objective and scope 9
3 Principles of measurement and interpretation 11 .1 Measurements 11 .2 Interpretation 15
4 Equipment specifications 17
6 Results 2 6.1 Length calibration 2
6.1.1 Caliper and SPR measurement 2 6.1.2 Estimated error in location of detected fractures 2
6.2 Electric conductivity and temperature 25 6.2.1 Electric conductivity and temperature of borehole water 25 6.2.2 Electric conductivity of fracture-specific water 25
6. Pressure measurements 26 6. Flow logging 26
6..1 General comments on results 26 6..2 Transmissivity and hydraulic head of borehole sections 27 6.. Transmissivity and hydraulic head of fractures 28 6.. Theoretical and practical measurement limits of flow
and transmissivity 29 6.5 Groundwater level and pumping rate 0
7 Summary 1
1 Introduction
The core drilled borehole KFM11A at Forsmark, Sweden was measured using Difference flow logging in two different time intervals between November 29 and December 12, 2006, and between April 17 and 19, 2007 (no successful measurements during the last interval). Difference flow logging is a swift method for a multifaceted characterization of a borehole. KFM11A is c. 851 m long and its inclination at the ground level is 60.9° from the horizontal plane. The location of KFM11A at Forsmark is illustrated in Figure 1-1. The borehole was drilled using a telescopic drilling technique, where the c. 0–71 m interval was percussion drilled and cased, and its inner diameter is c. 200 mm. A steel guide was inserted into the borehole between 67.7 m and 72.8 m. Below 72.8 m the borehole was core-drilled and its diameter is 77 mm. There was also an SKB dummy tool at the bottom of the borehole before any measurements were started. It was at approximately 88 m. The borehole was reinforced with metal at the intervals 97.–99. m, 521.55–52.55 m and 62.86–625.80 m after the first measurement period. The reinforcements had an inner diameter of 8 mm. The interval between 99.70–50.7 m was also widened to a diameter of approximately 8 mm.
The field work and the subsequent data interpretation were conducted by PRG-Tec Oy as Posiva Oy’s subcontractor. The Posiva Flow Log/Difference flow logging method has previously been employed in Posiva’s site characterisation programme in Finland as well as at the Äspö Hard Rock Laboratory at Simpevarp, Sweden. The commissions at the latter site included measurements in the 1,700 m long cored borehole KLX02 at Laxemar together with a methodology study /Ludvigson et al. 2002/.
This document reports the results acquired by the Difference flow logging method in the borehole KFM11A. The measurements were carried out as a part of the Forsmark site investigation and in accordance to SKB’s internal controlling document AP PF 00-06-096. The controlling documents for performing according to this activity plan are listed in Table 1-1. The list of the controlling documents excludes the assignment-specific quality plans. Both the activity plan and the method documents are SKB’s internal controlling documents. The measurement data and the results were delivered to the SKB site characterization database Sicada and are traceable by the activity plan number.
Table 11. SKB’s internal controlling documents for the activities concerning this report.
Activity plan Number Version Difference flow logging in borehole KFM11A AP PF 400-06-096 1.0
Method documents Number Version Method description for difference flow logging SKB MD 322.010e 1.0 Instruktion för rengöring av borrhålsutrustning och viss markbaserad utrustning
SKB MD 600.004 1.0
SKB MD 620.010e 2.0
SKB MD 320.004e 1.0
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Original data from the reported activity are stored in the primary database Sicada, where they are traceable by the Activity Plan number (AP PF 00-06-096). Only data in SKB’s databases are accepted for further interpretation and modelling. The data presented in this report are regarded as copies of the original data. Data in the databases may be revised, if needed. Such revisions will not necessarily result in a revision of the P-report, although the normal procedure is that major data revisions entail a revision of the P-report. Minor data revisions are normally presented as supplements, available at www.skb.se.
Figure 1-1. Location of the drill site DS11 at Forsmark and detailed maps of all the boreholes within the site.
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2 Objective and scope
The main objective of the difference flow logging in KFM11A was to identify water-conductive sections/fractures suitable for subsequent hydro-geochemical characterisation. Secondly, the measurements aimed at a hydrogeological characterisation, which includes the inspection of the prevailing water flow balance in the borehole and the hydraulic properties (transmissivity and undisturbed hydraulic head) of the tested sections. Based on the results of these investigations, a more detailed characterisation of flow anomalies along the borehole, e.g. an estimate of the conductive fracture frequency (CFF), may be obtained.
Besides difference flow logging, the measurement programme also included supporting measurements, performed in order to gain a better understanding of the overall hydrogeochemi- cal conditions. These measurements included the electric conductivity (EC) and the temperature of the borehole fluid as well as the single-point resistance of the borehole wall. The electric conductivity of a number of selected high-transmissive fractures in the borehole was also measured. Furthermore, the recovery of the groundwater level after pumping the borehole was registered and interpreted hydraulically.
A high-resolution pressure sensor was used to measure the absolute pressure along the borehole. These measurements were carried out together with the flow measurements. The results are used for the calculation of the hydraulic head along the borehole.
Single-point resistance measurements were also combined with caliper (borehole diameter) measurements to detect depth marks milled into the borehole wall at accurately determined positions. This procedure allowed for the length calibration of all other measurements.
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3 Principles of measurement and interpretation
3.1 Measurements Unlike traditional types of borehole flowmeters, the Difference flowmeter measures the flow rate into or out of limited sections of the borehole instead of measuring the total cumulative flow rate along the borehole. The advantage of measuring the flow rate in isolated sections is a better detection of the incremental changes of flow along the borehole, which are generally very small and can easily be missed using traditional types of flowmeters.
Rubber disks at both ends of the downhole tool are used to isolate the flow in the test section from that in the rest of the borehole, see Figure -1. The flow inside the test section goes through its own tube and passes through the area where the flow sensors are located. The flow along the borehole outside the isolated test section passes through the test section by means of a bypass pipe and is discharged at the upper end of the downhole tool. This entire structure is called the flow guide.
The Difference flowmeter can be used in two modes, a sequential mode and an overlapping mode. In the sequential mode, the measurement increment is as long as the section length. It is used for determining the transmissivity and the hydraulic head /Öhberg and Rouhiainen 2000/. In the overlapping mode, the measurement increment is shorter than the section length. It is mostly used to determine the location of hydraulically conductive fractures and to classify them based on their flow rates.
The Difference flowmeter measures the flow rate into or out of the test section by means of thermistors, which track both the dilution (cooling) of a thermal pulse and the transfer of a thermal pulse with moving water. In the sequential mode, both methods are used, whereas in the overlapping mode, only the thermal dilution method is used because it is faster than the thermal pulse method.
Figure 3-1. Schematic of the downhole equipment used in the Difference flowmeter.
WinchPump Computer
Flow sensor -Temperature sensor is located in the flow sensor
Single point resistance electrode
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Besides incremental changes of flow, the downhole tool of the Difference flowmeter can be used to measure:
• The electric conductivity (EC) of the borehole water and fracture-specific water. The electrode for the EC measurements is located on the top of the flow sensor, Figure -1.
• The single-point resistance (SPR) of the borehole wall (grounding resistance). The electrode of the single-point resistance tool is located in between the uppermost rubber disks, see Figure -1. This method is used for high resolution depth/length determination of fractures and geological structures.
• The diameter of the borehole (caliper). The caliper tool, combined with SPR, is used for the detection of the depth/length marks milled into the borehole wall. This enables an accurate depth/length calibration of the flow measurements.
• The prevailing water pressure profile in the borehole. The pressure sensor is located inside the electronics tube and connected via another tube to the borehole water, Figure -2.
• Temperature of the borehole water. The temperature sensor is located in the flow sensor, Figure -1.
All of the above measurements were performed in KFM11A.
The principles of difference flow measurements are described in Figures - and -. The flow sensor consists of three thermistors, see Figure -a. The central thermistor, A, is used both as a heating element and for the registration of temperature changes, Figures -b and c. The side thermistors, B1 and B2, serve to detect the moving thermal pulse, Figure -d, caused by constant power heating in A, Figure -b.
Figure 3-2. The absolute pressure sensor is located inside the electronics tube and connected through a tube to the borehole water.
Flow to be measured
Flow along the borehole
Cable
1
Time (s)
Thermal pulse method Temparature difference between B1 and B2
P1
1
Flow rate is measured during the constant power (P1) heating (Figure -b). If the flow rate exceeds 600 mL/h, the constant power heating is increased (to P2), Figure -b, and the thermal dilution method is applied.
If the flow rate during the constant power heating (Figure -b) falls below 600 mL/h, the measurement continues by monitoring transient thermal dilution (Figure -c) and thermal pulse response (Figure -d). When applying the thermal pulse method, thermal dilution is also measured. The same heat pulse is used for both methods.
The flow is measured when the tool is at rest. After the tool is transferred to a new position, there is a waiting time (the duration of which can be adjusted according to the prevailing circumstances) before the heat pulse (Figure -b) is applied. The waiting time after the constant power thermal pulse can also be adjusted, but it is normally 10 s long for thermal dilution and 100 s long for thermal pulse. The measurement range of each method is given in Table -1.
Figure 3-4. Flow measurement, flow rate > 600 mL/h.
0
50
100
150
200
132 000
54 900
24 800
13 100
6 120
3 070
1 110
P1
P2
a)
b)
c)
151050
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The lower end limits of the thermal dilution and the thermal pulse methods in Table -1 correspond to the theoretical lowest measurable values. Depending on the borehole conditions, these limits may not always prevail. Examples of disturbing conditions are floating drilling debris and gas bubbles in the borehole water, and high flow rates (above about 0 L/min) along the borehole. If the disturbing conditions are significant, a practical measurement limit is calculated for each set of data.
3.2 Interpretation The interpretation of data is based on Thiem’s or Dupuit’s formula that describes a steady state and a two dimensional radial flow into the borehole /Marsily 1986/:
hs – h = Q/(T·a) -1
where
h is the hydraulic head in the vicinity of the borehole and h = hs at the radius of influence (R),
Q is the flow rate into the borehole,
T is the transmissivity of the test section,
a is a constant depending on the assumed flow geometry. For cylindrical flow, the constant a is:
a = 2·π/ln(R/r0) -2
r0 is the radius of the well and
R is the radius of influence, i.e. the zone inside which the effect of the pumping is felt.
If flow rate measurements are carried out using two levels of hydraulic head in the borehole, i.e. natural or pump-induced hydraulic heads, then the undisturbed (natural) hydraulic head and transmissivity of the tested borehole sections can be calculated. Two equations can be written directly from equation -1:
Qs0 = Ts·a·(hs– h0) -
Qs1 = Ts·a·(hs– h1) -
where
h0 and h1 are the hydraulic heads in the borehole at the test levels,
Qs0 and Qs1 are the measured flow rates in the test section,
Ts is the transmissivity of the test section and
hs is the undisturbed hydraulic head of the tested zone far from the borehole.
Since, in general, very little is known of the flow geometry, a cylindrical flow without any skin zones is assumed. Cylindrical flow geometry is also justified because the borehole is at a constant head and there are no strong pressure gradients along the borehole, except at its ends.
Table 31. Ranges of flow measurements.
Method Range of measurement (mL/h)
Thermal dilution P1 30–6,000 Thermal dilution P2 600–300,000 Thermal pulse 6–600
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The radial distance R to the undisturbed hydraulic head hs is not known and must be assumed. Here a value of 500 is selected for the quotient R/r0. The hydraulic head and the test section transmissivity can be deduced from the two measurements:
hs = (h0–b·h1)/(1–b) -5
Ts = (1/a) (Qs0–Qs1)/(h1–h0) -6
where
b = Qs0/Qs1
The transmissivity (Tf) and hydraulic head (hf ) of individual fractures can be calculated provided that the flow rates of individual fractures are known. Similar assumptions as above have to be used (a steady state cylindrical flow regime without skin zones).
hf = (h0–b h1)/(1–b) -7
Tf = (1/a) (Qf0–Qf1)/(h1–h0) -8
where
Qf0 and Qf1 are the flow rates at a fracture and hf and Tf are the hydraulic head (far away from borehole) and transmissivity of a fracture, respectively.
Since the actual flow geometry and the skin effects are unknown, transmissivity values should be taken only as an indication of the orders of magnitude. As the calculated hydraulic heads do not depend on geometrical properties but only on the ratio of the flows measured at different heads in the borehole, they should be less sensitive to unknown fracture geometries. A discussion of potential uncertainties in the calculation of transmissivity and hydraulic head is provided in /Ludvigson et al. 2002/.
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4 Equipment specifications
The Posiva Flow Log/Difference flowmeter monitors the flow of groundwater into or out from a borehole by means of a flow guide (which uses rubber disks to isolate the flow). The flow guide thereby defines the test section to be measured without altering the hydraulic head. Groundwater flowing into or out from the test section is guided to the flow sensor. The flow is measured using the thermal pulse and/or thermal dilution methods. Measured values are transferred into a computer in digital form.
Type of instrument: Posiva Flow Log/Difference flowmeter.
Borehole diameters: 56 mm, 66 mm and 76–77 mm.
Length of test section: A variable length flow guide is used.
Method of flow measurement: Thermal pulse and/or thermal dilution.
Range and accuracy of measurement: See Table -1.
Additional measurements: Temperature, Single-point resistance, Electric conductivity of water, Caliper, Water pressure.
Winch: Mount Sopris Wna 10, 0.55 kW, 220V/50Hz. Steel wire cable 1,500 m, four conductors, Gerhard-Owen cable head.
Length determination: Based on the marked cable and on the digital length counter.
Logging computer: PC, Windows XP.
Software: Based on MS Visual Basic.
Total power consumption: 1.5–2.5 kW depending on the pumps.
Calibrated: August 2006.
Calibration of cable length: Using length marks in the borehole.
Range and accuracy of sensors is presented in Table -1.
Table 41. Range and accuracy of sensors.
Sensor Range Accuracy
Flow 6–300,000 mL/h ± 10% curr.value Temperature (middle thermistor) 0–50°C 0.1°C Temperature difference (between outer thermistors) –2 – + 2°C 0.0001°C Electric conductivity of water (EC) 0.02–11 S/m ± 5% curr.value Single point resistance 5–500,000 ± 10% curr.value Groundwater level sensor 0–0.1 Mpa ± 1% full-scale Absolute pressure sensor 0–20 MPa ± 0.01% full-scale
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5 Performance
5.1 General The Commission was performed according to Activity Plan AP PF 00-06-069 following the SKB Method Description 22.010, Version 1.0 (Method description for difference flow logging), see Table 1-1. The Activity Plan and the Method Description are both SKB’s internal controlling documents. Prior to the measurements, the downhole tools and the measurement cable were disinfected. Time was synchronized to local Swedish time. The activity schedule of the borehole measurements is presented in Table 5-1. The items and activities in Table 5-1 are the same as in the activity plan.
Logging cables, wires, and pipe strings are exposed to stretching when lowered into a vertical or sub-vertical borehole. This will introduce a certain error in defining the position of a test tool connected to the end of a logging cable. Immediately after completion of the drilling operations in borehole KFM11A, length marks were milled into the borehole wall at certain intervals to be used for length calibration of various logging tools. By using the known positions of the length marks, logging cables etc. can be calibrated in order to obtain an accurate length correction of the testing tool. Each length mark consists of two 20 mm wide tracks in the borehole wall. The distance between the tracks is 100 mm. The upper track defines a reference level.
The dummy logging (Item 8) of the borehole is done in order to assure that the measurement tools do not get stuck in the borehole. The dummy also collects solid material from the borehole wall. The solid material in the dummy is used for evaluation whether it is safe to continue with the other logging tools.
The Difference Flowmeter system uses caliper measurements in combination with single-point resistance measurements for detection of length marks (Item 9). These methods also reveal parts of the borehole widened for some reason (fracture zones, breakouts etc.). The length calibration of KFM11A was performed before any other measurements were started.
The electric conductivity (EC) and temperature of the borehole water (Item 10) during natural (un-pumped) conditions were measured after the calibration and dummy loggings.
The combined overlapping/sequential flow logging (Item 12) was carried out in the borehole with a 5 m section length and in 0.5 m length increments (step length). The measurements were performed during natural (un-pumped) conditions.
The telescopic part of the borehole was flow logged next (Item 11).
Pumping was started on December 6, 2006. After c. 18 hours waiting time, overlapping flow logging (Item 1) was conducted using the same section and step lengths as before.
The overlapping flow logging was then continued by re-measuring previously detected flow anomalies with a 1 m section length and a 0.1 m step length (Item 1). In this case there were so many anomalies that the entire measurable part of the borehole was measured.
The fracture specific EC of water from some selected fractures (Item 15) was also measured.
The EC of borehole water (Item 16) was measured while the borehole was still pumped. After this, the pump was stopped and the recovery of the groundwater level was monitored (Item 17).
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5.2 Nonconformities Item 8 was conducted several times because the dummy was not moving completely freely. The amount and size of the rock pieces that were collected on each run was also large. The complete history of the dummy loggings in given in Appendix 1. The part of the pipe and the metal pieces found during the dummy loggings were not left in the borehole by the devices used by PRG-Tec Oy. A magnetic brush logging by SKB and a dummy logging by SKB were also conducted as a part of the dummy loggings, see Appendix 1. SKB’s dummy tool ended up getting stuck in the borehole at approximately 500 m. Because of this, only the upper part of the borehole above the SKB dummy could be measured during the measurements in 2006.
Table 51. Flow logging and testing in KFM11A. Activity schedule.
Item Activity Explanation Date
none SKB’s magnetic brush logging Borehole stability/risk evaluation. 2006-12-01 8 Extra_2 Dummy logging Borehole stability/risk evaluation. 2006-12-01 8 Extra_3 Dummy logging Borehole stability/risk evaluation. 2006-12-01 8 Extra_4 Dummy logging Borehole stability/risk evaluation. 2006-12-02 8 Extra_5 Dummy logging Borehole stability/risk evaluation. 2006-12-02 8 Extra_6 Dummy logging Borehole stability/risk evaluation. 2006-12-02 9 Calibration SKB Caliper and SPR. Logging without the lower
rubber disks, no pumping. 2006-12-02– 2006-12-03
8 Extra_7 Dummy logging Borehole stability/risk evaluation. 2006-12-03 8 Extra_8 Dummy logging Borehole stability/risk evaluation. 2006-12-03 none SKB’s dummy logging Borehole stability/risk evaluation. 2006-12-04 8 Extra_9 Dummy logging Borehole stability/risk evaluation. 2006-12-05 10 EC- and temp-logging of
the borehole fluid Logging without the lower rubber disks, no pumping. 2006-12-05
12 Combined overlapping/ sequential flow logging
Section length Lw = 5 m, step length dL = 0.5 m, no pumping.
2006-12-05– 2006-12-06
Logging without the lower rubber disks, no pumping. 2006-12-06
13 Overlapping flow logging Section length Lw = 5 m, step length dL = 0.5 m, pumping (includes 1 day waiting after the pumping was started).
2006-12-06– 2006-12-07
14 Overlapping flow logging Section length Lw = 1 m, step length dL = 0.1 m, pumping.
2006-12-08– 2006-12-10
Section length Lw = 1.0 m, pumping, in pre-selected fractures.
2006-12-10
16 EC- and temp-logging of the borehole fluid
Logging without the lower rubber disks, pumping. 2006-12-11
17 Recovery transient Measurement of water level and absolute pressure in the borehole after the pumping was stopped.
2006-12-11– 2006-12-12
8B Extra_1 Dummy logging Borehole stability/risk evaluation. 2007-04-18 12 Combined overlapping/
sequential flow logging continued
Section length Lw = 5 m, step length dL = 0.5 m, no pumping. The measurement was not successful. The tool did not go deep enough.
2007-04-18– 2007-04-19
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It was planned that after the removal of the SKB dummy and the strengthening of the borehole, the measurements would be completed so that the part below c. 87 m could be measured. The second measurement campaign, in April 2007, was unsuccessful, because the dummy and the measurement tools did not go deeper than c. 500 m, see Appendix 1.
It was not physically possible to measure approximately 5.05 m above the SKB dummy, because there are weights and a centralizer in the measurement device. The rubber disks in the device must also be turned before the measurement begins. This reduces the measured distance by at least 50 cm.
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6 Results
6.1 Length calibration 6.1.1 Caliper and SPR measurement An accurate length scale for the measurements is difficult to achieve in long boreholes. The main cause of inaccuracy is the stretching of the logging cable. The stretching depends on the tension on the cable, the magnitude of which in turn depends, among other things, on the inclination of the borehole and the roughness (friction properties) of the borehole wall. The cable tension is larger when the borehole is measured upwards. The cables, especially new cables, may also stretch out permanently.
Length marks on the borehole wall can be used to minimize the length errors. The length marks are initially detected with the SKB caliper tool. The length scale is first corrected according to the length marks. Single-point resistance is recorded simultaneously with the caliper logging. All flow measurement sequences can then be length corrected by synchronising the SPR results (SPR is recorded during all the measurements except borehole EC measurements) with the original caliper/SPR-measurement.
The procedure of the length correction was the following:
• The caliper/SPR-measurements (Item 9) were initially length corrected in relation to the known length marks, Appendix 1.28, black curve. Corrections between the length marks were obtained by linear interpolation.
• The SPR curve of Item 9 was then compared with the SPR curves of Items 12, 1, 1, and 15 to obtain relative length errors of these measurement sequences.
• All SPR curves could then be synchronized, as can be seen in Appendices 1.2–1.27.
The results of the caliper and single-point resistance measurements from all measurements in the entire borehole are presented in Appendix 1.1. Five SPR-curves are plotted together with the caliper-data. These measurements correspond to Items 9, 12, 1, 1 and 15.
Zoomed results of the caliper and SPR data are presented in Appendices 1.2–1.27. The detectability of the length marks is listed in Table 6-1. All the length marks were at least partially detected by the caliper tool.
Most of the length marks were detected in the single-point resistance measurements. The SPR-anomaly is complicated due to the four rubber disks used at the upper end of the section, two at each side of the resistance electrode, but it is often possible to successfully detect the length marks even if the caliper tool has not found the marks.
The aim of the plots in Appendices 1.2–1.27 is to verify the accuracy of the length correction. The curves in these plots represent length corrected results. These appendices also illustrate a few locations where such SPR anomalies were found that could be used to help in determining the location of the measurement tool in the borehole.
The magnitude of length correction along the borehole is presented in Appendix 1.28. The negative values of the error represent the situation where the logging cable has been extended, i.e. the cable is longer than the nominal length marked on it.
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6.1.2 Estimated error in location of detected fractures In spite of the length correction described above, there can still be length errors due to the following reasons:
1. The point interval in the overlapping mode flow measurements is 0.1 m. This could cause an error of ± 0.05 m.
2. The length of the test section is not exact. The specified section length denotes the distance between the nearest upper and lower rubber disks. Effectively, the section length can be larger. At the upper end of the test section there are four rubber disks. The distance between them is 5 cm. This will cause rounded flow anomalies: a flow may be detected already when a fracture is situated between the upper rubber disks. These phenomena can cause an error of ± 0.05 m when the short step length (0.1 m) is used.
. Corrections between the length marks can be other than linear. This could cause an error of ± 0.1 m in the caliper/SPR-measurement (Item 9).
. SPR curves may be imperfectly synchronized. This could cause an error of ± 0.1 m.
In the worst case, the errors from sources 1, 2, and are summed and the total estimated error between the length marks would be ± 0. m.
The situation is slightly better near the length marks. In the worst case, the errors from sources 1, 2 and are summed and the total estimated error would be ± 0.2 m.
Knowing the location accurately is important when different measurements are compared, for instance flow logging and borehole TV. In that case the situation may not be as severe as the worst case above, since some of the length errors are systematic and the error is nearly constant in fractures that are close to each other. However, the error from source 1 is random.
Fractures nearly parallel with the borehole may also be problematic. Fracture location may be difficult to define accurately in such cases.
Table 61. Detected length marks.
Length marks given by SKB (m)
Length marks detected by caliper
Length marks detected by SPR
100 Both Yes 149.20 Both Yes 200 Both Yes 250 Both Yes 300 Both Yes 350 Both Yes 400 Both Yes 449 Both Yes 497 Both No 550 Both Yes 603 Both No 648 Only lower detected Yes 700 Both Yes 750 Only lower detected Yes
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6.2 Electric conductivity and temperature 6.2.1 Electric conductivity and temperature of borehole water The electric conductivity of the borehole water was initially measured when the borehole was at rest, i.e. at natural, un-pumped conditions. The measurement was performed downwards, see Appendices 2.1 (logarithmic scale) and 2.2 (linear scale), blue curve.
The EC measurement was repeated during pumping (after a pumping period of approximately five days), see Appendices 2.1 and 2.2, green curve.
The temperature of the borehole water was measured simultaneously with the EC measurements. The EC values are temperature corrected to 25°C to make them more comparable with other EC measurements /Heikkonen et al. 2002/. The temperature results in Appendix 2. have the same length axis as the EC results in Appendices 2.1 and 2.2.
The length calibration of the borehole electric conductivity measurements is not as accurate as in other measurements, because single-point resistance is not registered. The length correction of the SPR/caliper-measurement was applied to the borehole EC measurements, black curve in Appendix 1.28.
6.2.2 Electric conductivity of fracturespecific water The flow direction is always from the fractures into the borehole if the borehole is pumped with a sufficiently large drawdown. This enables the determination of electrical conductivity from fracture-specific water. Both electric conductivity and temperature of flowing water from the fractures were measured.
The fractures detected in the flow measurements can be measured for electrical conductivity later. These fracture-specific measurements begin near the fracture which has been chosen for inspection. The tool is first moved stepwise closer to the fracture until the detected flow is larger than a predetermined limit. At this point the tool is stopped. The measurement is continued at the given position allowing the fracture-specific water to enter the section. The waiting time for the EC measurement can be automatically calculated from the measured flow rate. The aim is to flush the water volume within the test section sufficiently to gain accurate results. The measuring computer is programmed so that the water in the test section will be replaced approximately three times over. After the set of stationary measurements, the tool is once again moved stepwise past the fracture for a short distance. The electric conductivity is also measured during the stepwise movement before and after the set of stationary measurements.
The test section in these measurements was 1 m long and the tool was moved in 0.1 m steps. The water volume in a one metre long test section is .6 L. The results are presented in Appendices 12.1–12.2. The blue symbol represents the conductivity value when the tool was moved and the red symbol is used for the set of stationary measurements.
The borehole lengths at the upper and lower ends of the section and the fracture locations as well as the final EC values are listed in Table 6-2.
For comparison, the fracture-specific EC and temperature results are also plotted with the EC and temperature results of borehole water, see Appendices 2.1–2..
26
6.3 Pressure measurements Absolute pressure was registered together with the other measurements in Items 11–15 and 17. The pressure sensor measures the sum of hydrostatic pressure in the borehole and air pressure. Air pressure was also registered separately, see Appendix 10.2. The hydraulic head along the borehole at natural and pumped conditions is determined in the following way. First, the monitored air pressure at the site is subtracted from the measured absolute pressure by the pressure sensor. The hydraulic head (h) at a certain elevation (z) is calculated according to the following expression /Nordqvist 2001/:
h = (pabs – pb)/ρfw g + z 6-1
where
h is the hydraulic head (m.a.s.l.) according to the RHB 70 reference system,
pabs is the absolute pressure (Pa),
pb is the barometric (air) pressure (Pa),
ρfw is the unit density, 1,000 kg/m
g is the standard gravity, 9.80665 m/s2 and
z is the elevation of measurement (m.a.s.l.) according to the RHB 70 reference system.
An offset of 2.0 kPa is subtracted from absolute pressure results.
The calculated head distributions are presented in Appendix 10.1. The exact z-coordinates are important in head calculation. A 10 cm error in the z-coordinate means a 10 cm error in the head.
6.4 Flow logging 6.4.1 General comments on results The measuring programme contained several flow logging sequences. They were gathered on the same diagram with single-point resistance (right hand side) and caliper plots (in the middle), see Appendices .1–.22. Single-point resistance is usually lower in value on a fracture where a flow is detected. There are also many other resistance anomalies caused by other fractures and geological features. The electrode of the single-point resistance tool is located within the upper rubber disks. Thus, the locations of the resistance anomalies of leaky fractures coincide with the lower end of the flow anomalies.
The caliper has been adjusted and specified to change its output from a high voltage value to a low voltage value between borehole diameters 77–78 mm.
Table 62. Fracturespecific EC.
Upper end of section (m)
Lower end of section (m)
Measured fracture (m)
EC (S/m) at 25°C
432.9 433.9 433.5 1.62 193.4 194.4 194.2 0.91 107.7 108.7 108.4 1.32 88.3 89.3 88.9 1.08 79.6 80.6 80.3 1.05 76.7 77.7 77.4 1.04
27
The flow logging was first performed with a 5 m section length and with 0.5 m length increments. The method (overlapping flow logging) gives the length and the thickness of conductive zones with a length resolution of 0.5 m. To obtain quick results, only the thermal dilution method was used for flow rate determination.
Under natural conditions or if the borehole isn’t pumped using a sufficient drawdown, the flow direction may be into the borehole or out from it. The direction of small flows (< 100 mL/h) cannot be detected in the normal overlapping mode (thermal dilution method). Therefore the measurement time was longer (so that the thermal pulse method could be used) at every 5 m interval in both 5 m section measurements. In the 1 m section measurements the thermal pulse method was also used, if it was deemed necessary based on the 5 m section measurements in pumped conditions. The thermal pulse method was only used to detect the flow direction.
The test section length determines the width of a flow anomaly of a single fracture. If the distance between flow yielding fractures is less than the section length, the anomalies will overlap, resulting in a stepwise flow data plot. The overlapping flow logging was therefore repeated in the vicinity of identified flow anomalies using a 1 m long test section and 0.1 m length increments.
The positions (borehole length) of the detected fractures are shown on the caliper scale. They are interpreted on the basis of the flow curves and therefore represent flowing fractures. A long line represents the location of a leaky fracture; a short line denotes that the existence of a leaky fracture is uncertain. The short line is used if the flow rate is less than 0 mL/h or the flow anomalies are overlapping or unclear because of noise.
The coloured triangles show the magnitude of the measured flows. The triangles have the same colour as the corresponding curves.
The flow along the borehole was also logged for the telescopic part of the borehole (Item 11). This was done by removing the lower rubber disks and guiding all flow along the borehole through the flow sensor. The locations of the measurements were at 71.0 m at the 86 mm metal tube and at 7.2 m at the intact bedrock just below the telescopic part of the borehole. The results are presented in Appendices 11.1 and 11.2. It can be seen from the data in both cases the water level changed a little and a detected flow upwards along the borehole dropped to zero within c. 20 minutes. It should be noted that the results at 71.0 m are uncertain since there is a risk that the rubber disks could permit some leakage in the measurements at the 86 mm metal tube.
The explanations to all the table headings and other symbols that are used in the appendices are given in Appendix .
6.4.2 Transmissivity and hydraulic head of borehole sections The borehole was flow logged with a 5 m section length and with 0.5 m length increments in both un-pumped and pumped conditions. All the flow logging results presented in this report are derived from the measurements that utilized the thermal dilution method to measure the flow rate.
The results of the measurements with a 5 m section length are presented in tables, see Appendix 5. Only the results with 5 m length increments are used. All borehole sections are shown in Appendices .1–.22. Secup and Seclow in Appendix 5 are the distances along the borehole from the reference level (top of the casing tube) to the upper end of the test section and to the lower end of the test section, respectively. The secup and seclow values for the two sequences (measurements at un-pumped and pumped conditions) are not exactly identical, due to a minor difference in the cable stretching. The difference between these two sequences was small. Secup and seclow given in Appendix 5 are calculated as the average of these two values.
28
Pressure was measured and calculated as described in Section 6.. h0FW and h1FW in Appendix 5 represent heads determined without and with pumping, respectively. The head in the borehole and calculated heads of borehole sections are given in RHB 70 scale.
The flow results in Appendix 5 (Q0 and Q1), representing the flow rates derived from measurements during un-pumped and pumped conditions, are presented side by side to make comparison easier. Flow rates are positive if the flow direction is from the bedrock into the borehole and vice versa. With the borehole at rest, 26 sections were detected as flow yielding, three of which had a flow direction from the borehole into the bedrock (negative flow). During pumping, all detected flows were directed towards the borehole.
It is also possible to detect the existence of flow anomalies below the measurement limit (0 mL/h = 8.·10–9 m/s), even though the exact numerical values below the limit are uncertain.
The flow data is presented as a plot, see Appendix 6.1. The left hand side of each diagram represents flow from the borehole into the bedrock for the respective test sections, whereas the right hand side represents the opposite. If the measured flow was zero (below the measurement limit), it is not visible in the logarithmic scale of the appendices.
The lower and upper measurement limits of the flow are also presented in the plots (Appendix 6.1). There are theoretical and practical lower limits of flow, see Section 6...
The hydraulic head and transmissivity (TD) of borehole sections can be calculated from the flow data using the method described in Chapter . The results are illustrated in Appendix 6.2. The hydraulic head of sections is presented in the plots if none of the two flow values at the same length is equal to zero. Transmissivity is presented if none or just one of the flows is equal to zero. The measurement limits of transmissivity are also shown in Appendix 6.2 and in Appendix 5. All the measurement limit values of transmissivity are based on the actual pressure difference in the borehole (h0FW and h1FW in Appendix 5).
6.4.3 Transmissivity and hydraulic head of fractures An attempt was made to evaluate the magnitude of fracture-specific flow rates. The results for a 1 m section length and 0.1 m length increments were used for this purpose. The first step in this procedure is to identify the locations of individual flowing fractures and then evaluate their flow rates.
In cases where the fracture distance is less than one metre, it may be difficult to evaluate the flow rate. There are such cases for instance in Appendix .2. In these cases a stepwise increase or decrease in the flow data plot equals the flow rate of a specific fracture (filled triangles in the appendices).
Since the 1 m long measurement section was not used during un-pumped conditions, the results for the 5 m section were used instead. The fracture locations are important when evaluating the flow rate in un-pumped conditions. The fracture locations are known on the basis of the 1 m section measurements. It is not a problem to evaluate the flow rate during un-pumped conditions when the distance between flowing fractures is more than 5 m. The evaluation may, however, be problematic when the distance between fractures is less than 5 m. In this case an increase or decrease of a flow anomaly at the fracture location determines the flow rate. However, this evaluation is used conservatively, i.e. only in the clearest of cases, and no flow value is usually evaluated during un-pumped conditions at densely fractured parts of bedrock. If the flow for a specific fracture can not be determined conclusively, the flow rate is marked with “–” and the value 0 is used in the transmissivity calculation, see Appendix 7. The flow direction is evaluated as well. The results of the evaluation are plotted in Appendix , blue filled triangle.
The total amount of detected flowing fractures was 92, but only 1 of them could be defined without pumping. These 1 fractures could be used for head estimations and all 92 were used
29
for transmissivity estimations. Transmissivity and hydraulic head of fractures are presented in Appendices 7 and 8.
Some fracture-specific results were classified to be “uncertain”. The basis for this classification is either a minor flow rate (< 0 mL/h) or unclear fracture anomalies. Anomalies are considered unclear if the distance between them is less than one metre or their nature is unclear because of noise.
Fracture-specific transmissivities were compared with transmissivities of borehole sections in Appendix 9. All fracture-specific transmissivities within each 5 m interval were first summed together to make them comparable with measurements with a 5 m section length. The results are fairly consistent between the two types of measurements. The decrease of flow as a function of pumping time can be seen in most fractures. The 1 m section measurements were carried out later than the 5 m section measurements and therefore flow rate and transmissivity are generally smaller in the 1 m section measurement results.
6.4.4 Theoretical and practical measurement limits of flow and transmissivity
The theoretical minimum of the measurable flow rate in the overlapping measurements (thermal dilution method only) is approximately 0 mL/h. The thermal pulse method can also be used. Its theoretical lower limit is about 6 mL/h. In this borehole the thermal pulse method was only used to detect the flow direction and not the flow rate. The upper limit of the flow measurements is 00,000 mL/h. These limits are determined on the basis of flow calibration. It is assumed that a flow can be reliably detected between the upper and lower theoretical limits during favourable borehole conditions.
In practice, the minimum measurable flow rate might, however, be much higher. Borehole conditions may have an influence on the base level of flow (noise level). The noise level can be evaluated on such intervals of the borehole where there are no flowing fractures or other structures. The noise level may vary along the borehole.
There are several known reasons for increased noise levels:
1) Rough borehole wall.
2) Solid particles in water such as clay or drilling debris.
) Gas bubbles in water.
) High flow rate along the borehole.
A rough borehole wall always causes a high noise level, not only in the flow results but also in the single-point resistance results. The flow curve and the SPR curves are typically spiky when the borehole wall is rough.
Drilling debris usually increases the noise level. Typically this kind of noise is seen in both un-pumped and pumped conditions.
Pumping causes the pressure to drop in the borehole water column and the water in the fractures near the borehole. This may lead to the release of dissolved gas and increase the amount of gas bubbles in the water. Some fractures may produce more gas than others. Sometimes the noise level is higher just above certain fractures (when the borehole is measured upwards). The reason for this is assumed to be gas bubbles. The bubbles may cause a decrease of the average density of water and therefore also decrease the measured head in the borehole.
The effect of a high flow rate along the borehole can often be seen above high flowing fractures. Any minor leak at the lower rubber disks is directly measured as increased noise.
A high noise level in a flow masks the “real” flow if it is smaller than the noise. Real flows are totally invisible if they are approximately ten times smaller than the noise and they are
0
registered correctly if they are approximately ten times larger than the noise. Based on experi- ence, real flows between 1/10 times the noise level and 10 times the noise level are summed with the noise. Therefore the noise level could be subtracted from the measured flow to get the real flow. This correction has not been done so far, because it is unclear whether it is applicable in each case.
The practical minimum of the measurable flow rate is evaluated and presented in Appendices .1–.22 using a grey dashed line (Lower limit of flow rate). The practical minimum level of the measurable flow is always evaluated in pumped conditions since this measurement is the most important for transmissivity calculations. The limit is an approxima- tion. It is evaluated to obtain a limit below which there may be fractures or structures that remain undetected.
The noise level in KFM11A was mostly 0 mL/h (150 mL/h on a short interval). It is possible to detect the existence of flow anomalies below the theoretical limit of the thermal dilution method (0 mL/h). The noise line (grey dashed line) was never drawn below 0 mL/h, because the values of flow rate measured below 0 mL/h are uncertain.
In some boreholes the upper limit of flow measurement (00,000 mL/h) may be exceeded. Such fractures or structures hardly remain undetected (as the fractures below the lower limit). High flow fractures can be measured separately at a smaller drawdown. The upper measurement limit was not exceeded in these measurements.
The practical minimum of measurable flow rate is presented in Appendix 5 (Q-lower limit P). It is taken from the plotted curve in Appendix (Lower limit of flow rate). The practical minimum of measurable transmissivity can be evaluated using Q-lower limit and the actual head difference at each measurement location, see Appendix 5 (TD-measlLP). The theoretical minimum measurable transmissivity (TD-measlLT) is evaluated using a Q value of 0 mL/h (minimum theoretical flow rate with the thermal dilution method). The upper measurement limit of transmissivity can be evaluated using the maximum flow rate (00,000 mL/h) and the actual head difference as above, see Appendix 5 (TD-measlU).
All three flow limits are also plotted with the measured flow rates, see Appendix 6.1. Theoretical minimum and maximum values are 0 mL/h and 00,000 mL/h, respectively.
The three transmissivity limits are also presented graphically, see Appendix 6.2.
Similar flow and transmissivity limits are not given for the fracture-specific results in Appendix 7. Approximately the same limits would though be valid also for these results. The limits for fracture-specific results are more difficult to define. For instance, it may be difficult to observe a small flow rate near (< 1 m) a high flowing fracture. The situation is similar for the upper flow limit. If there are several high flowing fractures less than one metre apart from each other, the upper flow limit depends on the sum of flows which must be below 00,000 mL/h.
6.5 Groundwater level and pumping rate The level of the groundwater table in the borehole during the measurement sequences is presented in Appendix 10.2. The borehole was pumped between December 6 and 11 with a drawdown of approximately 10 metres. The pumping rate was recorded, see Appendix 10.2.
The groundwater recovery was measured after the pumping period, between December 11 and 12, Appendix 10.. The recovery was measured with two sensors, the water level sensor (pressure sensor for monitoring water level) and the absolute pressure sensor located at the borehole length of 2.80 m.
1
7 Summary
In this study, the Posiva Flow Log/Difference Flow method has been used to determine the location and flow rate of flowing fractures or structures in borehole KFM11A at Forsmark, Sweden. Measurements were carried out both when the borehole was at rest and during pumping. A 5 m section length with 0.5 m length increments was used initially. The detected flow anomalies were then re-measured with a 1 m section and a 0.1 m measurement interval.
Length calibration was made using the length marks in the borehole wall. The length marks were detected by caliper and single-point resistance logging. The latter method was also performed simultaneously with the flow measurements, and thus all flow results could be length calibrated by synchronizing the single-point resistance logs.
The distribution of saline water along the borehole was logged by electric conductivity and temperature measurements of the borehole water. In addition, electric conductivity of fracture- specific water was measured in selected flowing fractures.
The water level in the borehole during the pumping and recovery period were measured.

Heikkonen J, Heikkinen E, Mäntynen M, 2001. Mathematical modelling of temperature adjustment algorithm for groundwater electrical conductivity on basis of synthetic water sample analysis. Helsinki, Posiva Oy. Working report 2002-10 (in Finnish).
Ludvigson J-E, Hansson K, Rouhiainen P, 2002. Methodology study of Posiva difference flow meter in borehole KLX02 at Laxemar. SKB R-01-52, Svensk Kärnbränslehantering AB.
Marsily G, 1986. Quantitative Hydrogeology, Groundwater Hydrology for Engineers. Academic Press, Inc., London.
Nordqvist R, 2001. Grundvattentryck – Inventering och utarbetande av rekommendationer för det geovetenskapliga undersökningsprogrammet. Djupförvarsteknik. SKB TD-0-01, Svensk Kärnbränslehantering AB.
Öhberg A, Rouhiainen P, 2000. Posiva groundwater flow measuring techniques. Helsinki, Posiva Oy. Report POSIVA 2000-12.
5
Appendices
Appendices 1.1–1.27 SPR and Caliper results after length correction
Appendix 1.28 Length correction
Appendix 2. Temperature of borehole water
Appendices .1–.22 Flow rate, Caliper and Single point resistance
Appendix Explanations for the tables in Appendices 5–7
Appendix 5 Table of transmissivity and head of 5 m sections
Appendix 6.1 Flow rates of 5 m sections
Appendix 6.2 Transmissivity and head of 5 m sections
Appendix 7 Table of transmissivity and head of detected fractures
Appendix 8 Transmissivity and head of detected fractures
Appendix 9 Comparison between section transmissivity and fracture transmissivity
Appendix 10.1 Head in the borehole during flow logging
Appendix 10.2 Air pressure, water level in the borehole and pumping rate during flow logging
Appendix 10. Groundwater recovery after pumping
Appendix 11.1 Vertical flow along the borehole at 71.0 m (measured at the 86 mm casing tube)
Appendix 11.2 Vertical flow along the borehole at 7.2 m
Appendices 12.1–12.2 Fracture-specific EC results
Appendices 1.1–1. Dummy logging 2006-11-29 – 2006-12-05
Appendix 1. Dummy/attempted flow logging 2007-0-17 – 2007-0-19
7
Flow rate (mL/h)
Caliper
SPR+Caliper, 2006-12-02 - 2006-12-03 SPR without pumping (L = 5 m), 2006-12-05 - 2006-12-06 SPR with pumping (upwards) (L = 5 m), 2006-12-07 SPR with pumping (upwards) (L = 1 m), 2006-12-08 - 2006-12-10 SPR with pumping (upwards during fracture-EC) (L = 1 m), 2006-12-10
Forsmark, borehole KFM11A SPR and Caliper results after length correction
8
Flow rate (mL/h)
Caliper
9
Flow rate (mL/h)
Caliper
0
Flow rate (mL/h)
Caliper
1
Flow rate (mL/h)
Caliper
2
Flow rate (mL/h)
Caliper

Flow rate (mL/h)
Caliper

Flow rate (mL/h)
Caliper
5
Flow rate (mL/h)
Caliper
6
Flow rate (mL/h)
Caliper
7
Flow rate (mL/h)
Caliper
8
Flow rate (mL/h)
Caliper
9
Flow rate (mL/h)
Caliper
50
Flow rate (mL/h)
Caliper
51
Flow rate (mL/h)
Caliper
52
Flow rate (mL/h)
Caliper
5
Flow rate (mL/h)
Caliper
5
Flow rate (mL/h)
Caliper
55
Flow rate (mL/h)
Caliper
56
Flow rate (mL/h)
Caliper
57
Flow rate (mL/h)
Caliper
58
Flow rate (mL/h)
Caliper
59
Flow rate (mL/h)
Caliper
60
Flow rate (mL/h)
Caliper
61
Flow rate (mL/h)
Caliper
62
Flow rate (mL/h)
Caliper
6
Flow rate (mL/h)
Caliper
6
Length error in logging cable (m)
SPR+Caliper (downwards), 2006-12-02 - 2006-12-03 SPR without pumping (L = 5 m), 2006-12-05 - 2006-12-06 SPR with pumping (upwards) (L = 5 m), 2006-12-07 SPR with pumping (upwards) (L = 1 m), 2006-12-08 - 2006-12-10 SPR with pumping (upwards during fracture-EC) (L = 1 m), 2006-12-10
Forsmark, borehole KFM11A Length correction
65
500
400
300
200
100
0
Forsmark, borehole KFM11A Electric conductivity of borehole water
Measured with lower rubber disks: Time series of fracture specific water, 2006-12-10 Last in time series, fracture specific water, 2006-12-10
66
0.5 1 1.5 2 2.5 Electric conductivity (S/m, 25 oC)
500
400
300
200
100
0
Forsmark, borehole KFM11A Electric conductivity of borehole water
67
500
400
300
200
100
0
Forsmark, borehole KFM11A Temperature of borehole water
69
Flow rate (mL/h)
Caliper
Without pumping (L=5 m, dL=5 m), (Flow direction = into the hole) Without pumping (L=5 m, dL=5 m), (Flow direction = into the bedrock) With pumping (L=5 m, dL=5 m), (Flow direction = into the hole) Without pumping (L=5 m, dL=0.5 m), 2006-12-05 - 2006-12-06 With pumping (Drawdown = 10 m, L=5 m, dL=0.5 m), 2006-12-07 With pumping (Drawdown = 10 m, L=1 m, dL=0.1 m), 2006-12-08 - 2006-12-10 With pumping during fracture-EC (Drawdown = 10 m, L=1 m, dL=0.1 m), 2006-12-10 Lower limit of flow rate
75.9
77.4
79.4
73.8
74.6
75.3
Forsmark, borehole KFM11A Flow rate, caliper and single point resistance
Fracture specific flow (into the hole) Fracture specific flow (into the bedrock)
70
Flow rate (mL/h)
Caliper
80.3
82.3
88.9
90.4
91.7
92.4
71
Flow rate (mL/h)
Caliper
100.3
104.4
105.5
107.1
108.4
109.2
113.0
114.6
116.2
112.0
111.7
119.1
100.5
72
Flow rate (mL/h)
Caliper
125.0
126.6
134.5
121.6
7
Flow rate (mL/h)
Caliper
140.1
146.7
151.0
152.0
154.2
155.4
157.1
158.5
7
Flow rate (mL/h)
Caliper
166.1
170.7
171.5
178.9
75
Flow rate (mL/h)
Caliper
194.2
76
Flow rate (mL/h)
Caliper
205.9
77
Flow rate (mL/h)
Caliper
78
Flow rate (mL/h)
Caliper
256.9 257.4
79
Flow rate (mL/h)
Caliper
261.5 262.0
80
Flow rate (mL/h)
Caliper
283.8
285.2
81
Flow rate (mL/h)
Caliper
82
Flow rate (mL/h)
Caliper
333.9
8
Flow rate (mL/h)
Caliper
8
Flow rate (mL/h)
Caliper
376.2
379.3
376.8
85
Flow rate (mL/h)
Caliper
397.9
395.3
86
Flow rate (mL/h)
Caliper
400.8
402.9
404.5
409.1
403.6
87
Flow rate (mL/h)
Caliper
420.2
426.1
427.2
428.0
432.5
433.5
436.2
438.1
433.9
436.6
88
Flow rate (mL/h)
Caliper
440.7
443.4
452.7
89
Flow rate (mL/h)
Caliper
467.6
475.7
474.6
90
Flow rate (mL/h)
Caliper
91
Appendix
Explanations
Header Unit Explanations
Borehole ID for borehole Secup m Length along the borehole for the upper limit of the test section (based on corrected length L) Seclow m Length along the borehole for the lower limit of the test section (based on corrected length L) L m Corrected length along borehole based on SKB procedures for length correction Length to flow anom. m Length along the borehole to inferred flow anomaly during overlapping flow logging Test type (1–6) (–) 1A: Pumping test – wire-line eq., 1B: Pumping test-submersible pump, 1C: Pumping test-airlift pumping, 2: Interference test, 3: Injection test,
4: Slug test, 5A: Difference flow logging -PFL-DIFF-Sequential, 5B: Difference flow logging -PFL-DIFF-Overlapping, 6: Flow logging-Impeller Date of test, start YY-MM-DD Date for start of pumping Time of test, start hh:mm Time for start of pumping Date of flowl., start YY-MM-DD Date for start of the flow logging Time of flowl., start hh:mm Time for start of the flow logging Date of test, stop YY-MM-DD Date for stop of the test Time of test, stop hh:mm Time for stop of the test Lw m Section length used in the difference flow logging dL m Step length (increment) used in the difference flow logging Qp1 m3/s Flow rate at surface by the end of the first pumping period of the flow logging Qp2 m3/s Flow rate at surface by the end of the second pumping period of the flow logging tp1 s Duration of the first pumping period tp2 s Duration of the second pumping period tF1 s Duration of the first recovery period tF2 s Duration of the second recovery period h0 m.a.s.l. Initial hydraulic head before pumping. Elevation of water level in open borehole in the local co-ordinates system with z = 0 m. h1 m.a.s.l. Stabilized hydraulic head during the first pumping period. Elevation of water level in open borehole in the local co-ordinates system with z = 0 m.
92
Header Unit Explanations
h2 m.a.s.l. Stabilized hydraulic head during the second pumping period. Elevation of water

forsmark site investigation â€“ difference flow logging

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